Two-photon chemistry of 1,8-bis(bromomethyl)naphthalene (la) and 1,8-bis(chloromethyl)naphthalene (Ib) was studied by (a) laser photolysis with use of XeCl (308 nm), KrF (248 nm), and ArF (193 nm) excimer lasers, (b) time-delayed, two-color photolysis with use of XeCl and XeF (351 nm) lasers, and (c) argon ion laser-jet (333, 351, and 364 nm) photolysis by both direct and benzophenone sensitization. The reaction proceeds through an intermediate monoradical 2, which is generated by a one-photon process, followed by additional photolysis to the two-photon product acenaphthene (4). On excitation of substrate 1 to its SI state, monoradical 2 is formed directly from the Si state and subsequently from the T-1 state through intersystem crossing, alternatively on benzophenone sensitization. Upper excited states, namely S-2 and S-3, of 1 are proposed in the KrF and ArF excimer laser irradiation, generating intermediate 2 through fast fragmentation of the T(sigma*) state. Transient targeting of intermediate 2 by time-delayed, two-color photolysis and argon ion laser-jet photolysis increases considerably the yield of the two-photon product 4.